1. Field of the Invention
The present invention pertains to a mechanical barrier which prevents tampering with storage tanks for fuels and other valuable liquids.
2. Description of the Related Art
U.S. Pat. No. 6,692,045, McCall, shows one of many approaches adopted to prevent tampering with the fill pipe, or stem, of an underground tank. FIG. 3 of McCall shows a cap (74) that is secured to the upper end of a stem (72). The retrofittable cap locking assembly, including a base portion (12), and a cover portion including a plate (18) and a flange (26), is fitted about the stem. A lock (40) passes through ears, or annular members (36, 38), to secure the cap locking mechanism in a fixed position around the cap (74).
U.S. Pat. No. 5,467,621, Gravino, discloses a closure (10) including a base (13) adapted to be screwed into a fuel tank filler pipe, and having a fill opening (18), normally closed by a hinged flapper valve (20), which is opened when a fuel nozzle is inserted into the fill opening. The base is shielded against being manually gripped and unscrewed from the filler pipe by a cover (30) also having a fill opening (34) and normally supported for free rotation on the base, so that turning of the cover is normally ineffective to unscrew the base.
Another approach to preventing tampering with filler pipes for storage tanks is disclosed in U.S. Pat. No. 8,240,500, Dalton et al. Dalton et al. discloses a lockable blocking plate (1) that is secured to a filler cap (3) for an underground storage tank. The locking mechanism is configured such that the lock (2) and the blocking plate may freely rotate with respect to the filler cap.
Numerous other approaches have been devised to prevent tampering with fuel storage tanks, which may contain gasoline, diesel fuel, oil, chemicals, or other valuable liquids. However, no one approach or structure has proven to be impenetrable to determined thieves armed with lock picking equipment, bolt cutters, pry bars, torches, and the like. Thus, the need for a relatively simple device of modest cost, which is easy to install and maintain, yet deters and/or defeats attempts to steal or tamper with the contents of underground tanks, remains unsatisfied.